Prior to 1980, little interest in numerical modeling existed in the field of hyperthermia; however, in the last several years numerical simulation of hyperthermia treatments has become one of the major areas of interest to hyperthermia researchers. The successes of recent numerical models in predicting the performance of certain therapy devices, prior to the accumulation of significant quantities of clinical data, have demonstration the impact that numerical simulation can have on the evaluation of existing therapy devices and the design and development of new clinical systems. While advancements have been made in the field of computer simulation of hyperthermia, this research area is still in its incipient stages, and a number of fundamental questions remain unanswered. This proposal identifies two such gaps in the state of existing knowledge which are basic to the continued clinical impact of numerical simulation: (1) the effects of detailed threedimensional numerical simulation on the evaluation, design, and development of hyperthermia therapy machines, and (2) the extent to which numerical models can predict specific power deposition patterns and resultant temperature distributions. To address these two areas where further study is needed, the specific aims proposed are: (1) to develop two and threedimensional numerical models of therapy devices to determine their dominant characteristics in the clinic, (2) to compare twodimensional numerical results with phantom and clinical measurements, (3) to compare twodimensional numerical calculations with results generated from full threedimensional numerical computations, and (4) to compare threedimensional numerical results with phantom and clinical measurements. Model developments will involve electromagnetic (EM) devices where finite, boundary, and hybrid element formulations will be used to solve the EM problem, and finite element and finite difference approaches will be used, when necessary, to compute temperature rise. The specific aims will also evaluate the clinical potential of numerical simulation for planning the treatment of a specific patient by systematic study of numerical results vs. phantom and clinical data. The University of Arizona Health Sciences Center has a variety of EM therapy devices (e.g. BSD Annular Phased Array, CDRH Helix, Phased Array Microwave System, etc.) which will be used for phantom experiments and clinical data. These studies will provide a scientific basis for the clinical applicability of numerical simulation in specific patient treatment planning.